After the governments of China and India, the Catholic Church is probably the third largest provider of K12 education in the world. How has growth in enrollment in K12 Catholic schools varied across countries over the last two decades? Which countries have accounted for most of the growth at the regional and global level? What has been the role of the number of schools and the size of schools in enrollment growth, or in the decline observed in some countries? Given trends towards higher enrollment in the developing world due to population growth and higher educational attainment, has enrollment growth in Catholic schools enabled them to maintain their market share over time? Finally, what do the data suggest for some of the constraints and strategic choices faced by Catholic schools in various countries? The objective of this paper is to answer these questions with a focus on trends in Catholic school enrollment and market shares across countries from 1995 to 2016.